A laboratory-scale gallery fire test on rubber conveyor belts with fabric skeletons

The authors have conducted a laboratory-scale gallery fire test on nine different rubber conveyor belts with fabric skeletons. The interior of the gallery used in this test was 2.5 m long, 0.35 m wide and 0.35 m high. The fire test on each sample was conducted in the upward airflow of the inclined gallery as well as in the horizontal one, and both 60 mm and 90 mm wide specimens, whose length was about 1.5 m, were provided for each test. The test results were compared with those from some other small-scale flammability tests; i.e. the small-scale flame, the oxygen index and the hot plate ignition tests. In addition, some problems in the laboratory-scale gallery fire test were also discussed. As a result, it has been found empirically that determination of both the time to ignition and the flame-propagation speed could be significant in case the flame propagated over the whole length of the belt specimen in the gallery, so that the fire resistance of the belt samples could be classified in detail.     

Problems in a drum friction test for fire-resistance evaluation of rubber conveyor belts with fabric skeletons

A drum friction test was conducted on four different ‘flame-resistant’ and one ‘non-flame-resistant’ rubber conveyor belts with a fabric skeleton manufactured in Japan. These test results were compared with those obtained from the other flammability tests, i.e. a small-scale flame test, an oxygen index test and a laboratory-scale gallery test, and both sample and rank correlation coefficients were calculated. As a result, the authors have concluded that fire resistance of belting materials themselves could not be adequately assessed by the results from the drum friction test, which could have some significance only when other combustible materials exist near the drive pulleys or idlers of belt conveyors.     

Effect of calcium carbonate filler on the fire and smoke properties of moulded polypropylene

‘Oxygen Index’, ‘Rate of Burning and Extent of Burning of Self-supporting Plastics in a Horizontal Position’ and ‘Vertical Flammability’ tests were used for examination of polypropylene copolymer HW 607M and the same copolymer filled with 40% w/w calcium carbonate. Room-scale studies were also carried out using a range of standard ignition sources. In the latter tests, measurements of the levels of smoke generated in the test chamber were monitored continuously, and intermittent measurements were made of the carbon monoxide concentrations. Small-scale testing showed that addition of the filler to the polypropylene raised the limiting oxygen index of the polymer from 17.8 to 20.3, which is only marginally lower than the oxygen concentration in ambient air (20.9); this introduces the possibility of a filled polypropylene which is not ignitable in air. However, the results of the UL94 and ASTM D635 tests did not show significant differences in flammability and rates of vertical and horizontal flame spread as between the two materials, through the unfilled polymer produced extensive burning droplets early in both tests whilst the filled polymer did not. Such droplets can spread fires to floor coverings, so that the filled plastic might be preferable in application. In our laboratory tests, the filled samples gave considerably lower smoke generation than the unfilled ones. At high heat fluxes they generated considerably less smoke than (smaller) unfilled samples containing the same mass of polymer. This suggests that the calcium carbonate has specific smoke-suppressant activity and is not merely acting as a polymer diluent. In larger-scale tests, unfilled samples were readily ignited by a domestic match, whilst the filled samples required an ignition source of 43 kJ (some six times greater than the match source) in order to light them and sustain ignition. The filled polymer did not melt on ignition and there was no lateral spread of flame from the sample. Smoke generation was considerably lower, the average optical density at maximum obscuration being 0.27, compared with 0.84 for the unfilled control. In particular, smoke suppression achieved by use of calcium carbonate at higher heat-flux levels is considerably greater than that expected for an inert diluent.     

A small-scale flame test for fire-resistance evaluation of rubber conveyor belts with fabric skeletons

Small-scale flame tests were conducted on samples of six different rubber conveyor belts with fabric skeletons for use in Japanese coal mines. Each sample was claimed to be ‘flame-resistant’ under the test condition prescribed in JIS K 6324-1977, but results show that there are problems in this kind of test. Every sample tested sustains flame continuously when the flame exposure time exceeds a certain value or ‘ignition time’. In addition, flame duration seems to depend on the flame-resistance of the fabric skeleton as well as on flame exposure time.     

乳胶泡沫引火位置对火蔓延特性的影响

利用自行搭建的小尺寸实验平台,开展了对不同点火位置的乳胶泡沫材料燃烧过程的对比实验,通过对火蔓延过程中的部分重要参数（如最大火焰高度、火蔓延速度和蔓延过程中样品表面温度变化等）的测定,分析了点火位置不同时,乳胶泡沫材料的火蔓延特性。结果表明：边缘点火和中间点火条件下,最大火焰高度分别为397和491 mm,火蔓延速度分别为1.8和0.97 mm·s^-1;边缘点火时的乳胶泡沫材料表面火蔓延过程中的温度低于中间点火情况下。     

Smoldering combustion of rice husk dusts on a hot surface

An accumulated combustible dust layer on some hot process equipment, such as grinders, dryers, hot bearings, etc., can be ignited and lead to fires if the hot surface temperature is sufficiently high. Experimental tests are used to determine the minimum hot surface temperature for dust ignition, the ignition temperature of dust itself, and the ignition times in this study. Egyptian rice husk dust is sieved into different sizes (particle diameters) to be used in this investigation. The effects of the dust particle size and the sample size (depth of the dust layer) on ignition parameters are tested. The boundary between the ignition and non-ignition conditions is investigated precisely through a large number of tests. The results show that the minimum hot plate temperature for ignition of dusts decreases as the dust layer depth increases.     

Long-term reproducibility of small-scale tests used for measuring the flammability of conveyor belting

Three small-scale flammability tests were evaluated for potential use in quality control. The small-scale flame test produced excessive scatter of data, the hot-plate ignition test gave reasonably reproducible data, but the critical oxygen index yielded superior results and is recommended for quality control testing.     

Correlation between the critical oxygen index test and other fire tests

The Critical Oxygen Index test is widely used as a measure of the flammability of many substances. This paper reviews attempts that have been made to compare Oxygen Index values with the results from other fire tests. Varying degrees of correlation are apparent, depending on the properties being measured in the respective tests.     

The Accumulation of Flammable Gases in Cone Calorimeter Tests is Responsible for Flash Ignition of Wool and Cotton Samples

In this paper a possible explanation is presented for the differences found between the fire behaviour of materials in small-scale cone calorimeter tests and the large-scale furniture calorimeter. The results obtained with cone calorimeter/FTIR equipment at 35 kW m⁻² will show that the early flash ignitions of typical materials like cotton and wool are due to the liberation of flammable gases during the pyrolysis phase and the typical ignition situation on the cone calorimeter, that is, the presence of a sparking igniter above the sample. This fast flash ignition and the early heat release behaviour on the cone calorimeter may be in contradiction to the early fire growth in other fire tests where the ignition conditions are clearly different from pyrolysis circumstances, that is, ignition via a burning newspaper, match, gas flame, etc.     

Evaluation of laboratory gallery fire tests of conveyor belting

Two mid-scale laboratory gallery fire tests, the propane gallery and the BELT test, were constructed and evaluated. In both cases the fundamental parameter that can be used for ranking flammability of a belting is the total quantity of heat input into the sample, rather than length burned or flame-out time. The temperature and velocity of the ventilating air used were found, experimentally and theoretically, to be critical factors in determining the results of the tests. The two tests correlated qualitatively on a pass|fail basis; however, the BELT test was affected more by the thickness of the sample: the thicker, the more probable to pass the test. The BELT test has the advantages of easier control and producing fewer pollutants. The results of BELT, propane gallery and critical oxygen index tests on some beltings are compared.     

Ignition performance of new and used motor vehicle upholstery fabrics

This paper examines the standards for fire safety in transport systems and in particular the test method for the flammability of materials within passenger compartments of motor vehicles. The paper compares data from ignition tests conducted in the cone calorimeter and the FIST apparatus with tests conducted using the FMVSS 302 horizontal flame spread apparatus. Ten materials were selected as representative of those used as seat coverings of private and commercial passenger vehicles. The time to ignition of new and used materials subject to exposure heat fluxes between 20 kW/m² and 40 kW/m² was measured. The results from the ignition tests were analysed using thermally thick and thermally thin theoretical models. The critical heat flux for sustained piloted ignition was determined from the time to ignition data using the thermally thin approach. Derived ignition temperatures from both the thermally thick and thermally thin methods were compared with measurements using a thermocouple attached to the back surface of materials in selected tests. The flame spread rates in the FMVSS 302 apparatus were determined and a comparison was made between the performance of the materials in the flame spread apparatus, the cone calorimeter and the FIST. The results suggests that a critical heat flux criterion could be used to provide an equivalent pass/fail performance requirement to that specified by the horizontal flame spread test although further testing is needed to support this. Copyright © 2004 John Wiley & Sons, Ltd.     

Flame retardancy finish with an organophosphorus retardant on silk fabrics

The paper mainly deals with flame retardancy of silk fabrics treated with a commercial organophosphorus flame retardant [N‐hydroxymethyl (3‐dimethyl phosphono) propionamide (HDPP), also known as Pyrovatex CP], using the pad‐dry‐cure‐wash method. The structures and properties of the treated and control sample are discussed. The Limiting Oxygen Index (LOI) value of the modified sample is above 30%. After 50 laundry cycles, it still has some flame retardancy left. HDPP and a cross‐linking agent (HMM) were bound to silk fabrics which is confirmed by FT‐IR spectra and amino analysis. The reaction degree of the flame retardant with silk is also high; almost all the tyrosine units have reacted, which can be confirmed by amino acid analysis. The reaction between flame retardant and silk only occurs in the amorphous region of silk fibre, which is confirmed by X‐ray diffraction analysis and amino acid analysis. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis show that the flame retardant causes silk fabrics to decompose below its ignition temperature (600°C) and formed carbonaceous residue or char when exposed to fire. The char behaves as a thermal barrier to fire, so silk fabrics show good flame retardancy. The treatment has a little effect on the whiteness of the silk fabrics and the tensile strength of treated silk fabrics slightly decreased; both effects are negligible. Copyright © 2006 John Wiley & Sons, Ltd.     

Ignition and flame propagation of electric cables in a laboratory-scale gallery fire test

The authors have conducted a laboratory-scale gallery fire test on eight different samples of electric cable in a horizontal airflow. The number of speciments and the distances between them on the trestle were varied for each test. As a result, it was found that both ignitability and flame-propagation properties depended on the distance between the specimens as well as on their number. Such flammability properties obtained for each cable sample were also found to be considerably consistent with the critical oxygen index. In addition, it is proposed that the flammability should be classified largely into five categories in this laboratory-scale gallery fire test for fire-retardance evaluation of solid combustible materials such as electric cables.     

Study of coal and coke ignition in fluidized beds

Ignition tests were conducted with delayed and fluid petroleum cokes, a high volatile bituminous coal and their blends in bench- and pilot-scale fluidized bed combustors. In the bench-scale FBC tests, a visual inspection ignition criterion was developed based on the ‘CO–CO₂’ profiles obtained as a function of time and bed temperature. In the pilot-scale unit, the rapid increase in SO₂ levels was used as the indicator of fuel ignition. In addition to the fluidized bed ignition tests, thermogravimetric analysis (TGA) measurements were made on all fuels and their chars. The results showed that, while the fluid coke (which has the lowest volatile content) was the most difficult to ignite, ignition was not a simple function of volatile content. Further, different test methods and ignition criteria demonstrated significantly different ignition temperatures, with the largest variation arising between bench- and pilot-scale equipment. Finally, tests on mixtures of petroleum coke and coal showed that there was no interaction between these two fuels, and that the coke ignited only when it achieved its own ignition temperature.     

Impact of air velocity on ignition in the Intermediate Scale Calorimeter (ICAL)

Higher surface temperatures were required for ignition in the Intermediate Scale Calorimeter than in the Cone Calorimeter. Air velocity measurements were made in front of calcium silicate and particleboard specimens in the Intermediate Scale Calorimeter and temperature measurements were carried out on their exposed surfaces. The higher ignition temperature in the Intermediate Scale Calorimeter was the result of the high induced upward air velocity due to the large specimen size (1.0 m by 1.0 m). This caused the flame to blow off. A higher surface temperature was needed to produce a downward flame spread rate sufficient to overcome the upward air velocity. To counteract this effect, a horizontal projection plate extending 100 mm out from the bottom edge of the specimen was installed. This created an eddy, causing a downward air velocity near the surface at the bottom of the specimen. The igniter was a hot wire across the width of the specimen at a height of 100 mm. The flame quickly spread down from the igniter to the bottom edge and attached there. Under these conditions the temperature required for ignition of particleboard in the Intermediate Scale Calorimeter was less than it was in the Cone Calorimeter. © 1997 John Wiley & Sons, Ltd.     

Ignition kernel development studies relevant to lean-burn natural-gas engines

In lean-burn premixed natural-gas engines, ignition and combustion can be accelerated by burning a small fraction of the mixture in a pre-chamber. High pressure generated in the pre-chamber results in the discharge of burned products into the main chamber. This creates multiple ignition kernels along the surface of the resulting jet. In this work, lean-burn characteristics of methane under the high pressure and high temperature conditions of a hot-jet ignited combustion chamber are investigated numerically by initializing a kernel of specified composition, temperature and size in a lean premixed gas, and following the development of the flame. In the case of hot-jet ignition the kernel temperature is limited by the temperature of the hot products. The influence of variations in ignition energy, affected by both temperature and size, and equivalence ratio, on the flame development is studied in an initially quiescent gas. It is shown that as long as the available ignition energy is greater than a minimum, the duration in which a steady flame speed is achieved is a strong function of kernel temperature; it is not a function of kernel size.     

Flammability characteristics at applied heat flux levels up to 200 kW/m2

This paper documents the first of the two interrelated studies that were conducted to more fundamentally understand the scalability of flame heat flux, the motivation being that it has been reported that flame heat flux back to the burning surface in bench‐scale experiments is not the same as for large‐scale fires. The key aspect was the use of real scale applied heat flux up to 200kW/m² which is well beyond that typically considered in contemporary testing. The main conclusions are that decomposition kinetics needs to be included in the study of ignition and the energy balance for steady burning is too simplistic to represent the physics occurring. An unexpected non‐linear trend is observed in the typical plotting methods currently used in fire protection engineering for ignition and mass loss flux data for several materials tested and this non‐linearity is a true material response. Using measured temperature profiles in the condensed phase shows that viewing ignition as an inert material process is inaccurate at predicting the surface temperature at higher heat fluxes. The steady burning temperature profiles appear to be invariant with applied heat flux. This possible inaccuracy was investigated by obtaining the heat of gasification via the ‘typical technique’ using the mass loss flux data and comparing it to the commonly considered ‘fundamental’ value obtained from differential scanning calorimetry measurements. This comparison suggests that the ‘typical technique’ energy balance is too simplified to represent the physics occurring for any range of applied heat flux. Observed bubbling and melting phenomena provide a possible direction of study. Copyright © 2007 John Wiley & Sons, Ltd.     

Ignition of exterior building details in bushfires: An experimental study

A laboratory study of the ignition of building details incorporating timber, under bushfire conditions, using ‘mock-ups’ of these details and both realistic (leaves and twigs) and, mainly, artificial (cribs) ignition sources has been carried out. Parameters such as mock-up type, moisture content of the timber comprising the mock-ups, and temperature and relative humidity of the experimental atmosphere were examined. It was found that all these parameters affected the ignition and flame propagation induced and that under conditions typical of a severe bushfire, only very small amounts of fuel were required to cause ignition. These results support the belief, based on field studies, that ignition of exterior building details composed of timber plays an important role in the destruction of buildings in bushfires.     

Moving wire technique studies of ablation,ignition and extinction of polymer flames

A new experimental method for studying the ablation, ignition and extinction of polymers exposed to flames and other ignition sources is presented. The technique is called the ‘Moving Wire Technique’. The polymer sample is carried on a wire support which is moved uniformity through the ignition source which is a flame in the example given. In the laboratory coordinate system, points along the path of the wire correspond to increasing residence time. The polymer combustion thus becomes a steady-state phenomena which can be studied at leisure with the improvements in precision associated with long time steady-state measurements. In addition to steady-state combustion, ignition and extinction transitions are observed whose onsets are sharp and can be accurately characterized in this system. In a favorable case, a reproducibility of a few parts per thousand is attained in determining critical ignition exposure times and extinction velocities. Results from initial studies of commercial Teflon® and poly-(vinylchloride) are presented. Measurements include critical ignition times and extinction velocities a function of free oxygen concentration. For poly-(vinylchloride), measurements are given of gas phase composition, mass loss of the polymer, and surface temperature of the polymer as a function of exposure time. A discussion is given of the relation of the results to other experiments and potential uses of the technique.     

A study of fire performance of textile membranes used as building components

The advantages of textile materials as building components include low weight, and in the case of textile membranes, the advantages include translucency and architectural possibilities. A common disadvantage, however, is the fire property of textile materials, which highlights the importance of fire safety assessments for building application of such materials. The work presented in this paper was conducted within the European project contex‐T, ‘Textile Architecture – Textile Structures and Buildings of the Future’. This paper presents the results of reaction‐to‐fire tests required for European Standard (EN) 13501–1 classification conducted with a number of textile membranes. The classification results are compared for a selection of these membranes with the information gained from a large‐scale reference test that was designed within the project. The reference test was based on the International Organization for Standardization (ISO) 9705 room test. It was seen that the reference test could separate the performance of the different types of membranes investigated and the repeatability of duplicate tests performed was acceptable. However, the classification of the materials by test results from the Single Burning Item (SBI) test (EN 13823) and the small flame test (EN ISO 11925–2) did not reflect the performance of the membranes in the large‐scale test properly in all aspects important for fire safety. Most significantly, the ‘burn‐through’ and the associated opening of a hole in the polyvinyl chloride/polyester membranes tested ventilated the hot smoke gases out of the reference room that resulted in limited flame spread and heat production. This mechanism is not modelled correctly by the SBI test, which leads to a discrepancy between classification and large‐scale behaviour. Copyright © 2011 John Wiley & Sons, Ltd.